During operation of an internal combustion engine fuel can be pushed into the small gap between the piston and the cylinder wall during a compression stroke. During the next expansion stroke fuel remains trapped in the small gap and does not combust. Only during a subsequent exhaust stroke may the trapped fuel escape from the gap into the cylinder. The released fuel will flow into the exhaust system instead of being ignited during an expansion stroke. As a result, engine emissions may be increased and engine efficiency and fuel economy may be decreased.
As such in one approach, an engine system is provided. The engine system includes a first piston movable within a cylinder, a second piston movable within a hollow body of the first piston, the movement defining a boundary of a reservoir within the hollow body, a spring device coupled to the first piston and the second piston, and a vent passage fluidically connecting the reservoir to the cylinder. In this way, the vent passage can provide fluidic communication between the reservoir and cylinder to enable the reservoir to receive gases, such as hydrocarbons, during an exhaust stroke and release the gases during a subsequent expansion stroke. Consequently, hydrocarbons, which in previous engines would be released into the cylinder during an exhaust stroke, can be stored in the reservoir and released during desired combustion cycle phases. As a result, engine emissions are reduced.
The inventors herein have recognized the above issues and potential options to address them. The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.